For a semiconductor package that includes at least one semiconductor die therein, particularly for power integrated circuits (ICs), the problem of heat dissipation is an important issue. A semiconductor package with poor heat dissipation may not just produce errors, but may also reduce product reliability and greatly increase manufacturing cost.
One known power package that includes enhanced cooling is an exposed heat slug package that comprises a heat slug (e.g., copper slug) that is exposed on the bottomside of the package. The die is bonded face (active topside) up on top of the heat slug with a thermally conductive die attach material. Another known power package is an exposed silicon package that flip chip mounts the semiconductor die on a die pad and exposes the bottomside of the semiconductor die. A heat sink is then thermally coupled to the bottomside of the semiconductor die using a thermal grease.
Both of these known power packages have significant thermal resistance that reduces cooling performance due to multiple interfaces in the cooling path that increases the thermal resistance of the package. For example, the exposed heat slug package includes the semiconductor substrate (e.g., silicon), the die attach material, the heat slug and solder in the cooling path from the topside of the semiconductor to an underlying workpiece, such as a printed circuit board (PCB). Similarly, the exposed silicon package includes the substrate, thermal grease and the heat sink in the cooling path from the topside of the semiconductor die to the atmosphere.